IL-6 is a pleiotropic proinflammatory cytokine produced and secreted by a wide variety of cell types most notably antigen presenting cells, T and B cells. IL-6 is involved in such diverse activities as B cell growth and differentiation, T cell activation, hematopoiesis, osteoclast activation, keratinocyte growth, neuronal growth and hepatocyte activation. IL-6 binds to transmembrane or soluble IL-6R and signals through gp130, which is shared by several other cytokines.
IL-6 plays an important role in B cell abnormalities as demonstrated in systemic lupus erythematosus, multiple myeloma and lymphoproliferative disorders. Similarly, IL-6 is also implicated in the pathogenesis of autoimmune and inflammatory diseases such as rheumatoid arthritis and osteoarthritis. Recently, indirect evidence suggests an association between IL-6 and chronic obstructive pulmonary disease and insulin resistance in type 2 diabetes. IL-6 has both pro-inflammatory and anti-inflammatory effects in the immune system, indicating that this cytokine likely plays a central role in regulating the physiological response to disease. Therefore, targeting IL-6 can potentially provide therapeutic benefit in a variety of disease areas.
An increase in the production of IL-6 has been observed in a number of diseases including: Alzheimer's disease, autoimmune diseases, such as rheumatoid arthritis, inflammation, myocardial infarction, Paget's disease, osteoporosis, solid tumors (renal cell carcinoma), prostatic and bladder cancers, neurological cancers, and B-cell malignancies (e.g., Casteleman's disease, certain lymphomas, chronic lymphocytic leukemia, and multiple myeloma). Research has indicated that IL-6 is linked to the pathogenesis of many of these diseases, particularly, cancer and, therefore, blocking IL-6 should translate into clinical benefits.
Murine, chimeric, and other non-human anti-IL-6 antibodies have been developed; however, they may be limited in their potency, effectiveness, may often trigger an unacceptable immune response (i.e., immunogenicity) and/or require a high dosage (See, Trikha et al., Clin. Can. Res. 9, 4653-4665, October 2003, herein incorporated by reference). For example, antibodies containing non-human portions often give rise to an immune response in humans. Accordingly, repeated antibody administration is unsuitable as therapy and immune complex mediated clearance of antibodies from circulation can reduce the potency/effectiveness of the antibody. Serum sickness and anaphylaxis are two exemplary conditions that may be caused by repeat administration of antibodies having non-human portions. In this regard, an anti-IL-6 antibody with less potential for immunogenicity, i.e., more tolerable in humans, and that is more potent such that it requires a smaller dosage as compared to previously used anti-IL-6 antibodies is needed.